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Lining of waste storage and disposal sites is a common practice to prevent hazardous waste constituents from migrating out of the facility into the surrounding environment. Recently, geomembranes have been widely used to line the waste storage and disposal sites and are expected to be even more common in the future. However, there are not enough data available on the mass transport of organic chemicals through geomembranes by the physicochemical process of partition and diffusion. In this study, partition and diffusion coefficients were measured using a gravimetric method for high-density polyethylene (HDPE) geomembrane in acetone, chlorobenzene, ethyl acetate, ethylbenzene, nhexane, methylene chloride (MC), n -octane, toluene, trichloroethylene (TCE), and m-xylene. Sorption tests were also conducted with mixtures of TCE, MC, toluene, gasoline, and aqueous solutions of TCE, MC, toluene, and w-xylene. The effect of geomembrane thickness on the mass flux parameters was also evaluated.A mathematical model with a time-dependent diffusion coefficient successfully simulated sorption curves of pure chemicals. The partition and diffusion coefficients of individual organic compounds in a mixture were accurately predicted from the mass-transport parameters of indi vidual pure chemicals by multiplying them with their mole fractions. Low-density polyethylene geomembranes had approximately 4 times and 10 times greater partition and diffusion coefficients than HDPE geomembranes, respectively. A mathematical model together with the experimentally determined parameters was used to predict the mass flux of selected organic chemicals present in gasoline through a 10.2-cm (4-in.) HDPE pipe (0.4-cm [0.16-in.] thick). Water Environ. Res., 65, 227 (1993).

A new way of generating Class A sludge using microwaves was evaluated through a series of laboratory‐scale experiments. Microwaves provide rapid and uniform heating throughout the material. Other benefits of microwave treatment include instant and accurate control and selective and concentrated heating on materials, such as sludge, that have a high dielectric loss factor. Sludge was irradiated with 2450‐MHz microwaves, and fecal coliforms were counted. Fecal coliforms were not detected at 65°C for primary sludge and anaerobic digester sludge and at 85°C for waste activated sludge when sludge was irradiated with 2450‐MHz microwaves. During the bench‐scale anaerobic digester operation, the highest average log reduction of fecal coliforms was achieved by the anaerobic digester fed with microwave‐pretreated sludge (≥2.66 log removal). The anaerobic digester fed with microwave‐irradiated sludge was more efficient in inactivation of fecal coliforms than the other two digesters fed with raw sludge and externally heated sludge, respectively. It took more than three hydraulic retention times for a bench‐scale mesophilic anaerobic digester to meet Class A sludge requirements after feeding microwave‐irradiated sludge. Class A sludge can be produced consistently with a continuously fed mesophilic anaerobic digester if sludge is pretreated with microwaves to reach 65°C.

Fluorescent lamps rely on mercury as the source of ultraviolet radiation for the production of visible light. Partitioning of mercury among vapor phase, loose phosphor powders produced during breaking and washing steps, glass matrices, phosphor powders attached on the glass and aluminum end caps was examined from simulated laboratory lamp recycling tests for different types of spent and new fluorescent lamps. Mercury concentrations in lamp glasses taken from commercial lamp recyclers were also analyzed for comparison with the simulated results of spent and new lamps of different types. The mercury content of the glass from spent lamps was highly variable depending on the lamp type and manufacturer; the median values of the mercury concentration in glasses for spent 26- (T8) and 38-mm (T12) diameter fluorescent lamps were approximately 30 and 45 microg/g, respectively. The average mercury concentration of samples taken from recycler A was 29.6 microg/g, which was about 64% of median value measured from the spent T12 lamps. Over 94% of total mercury in lamps remained either as a component of phosphor powders attached inside the lamp or in glass matrices. New T12 lamps had a higher partitioning percentage of elemental mercury in the vapor phase (0.17%) than spent T12 lamps (0.04%), while spent lamps had higher partitioning percentages of mercury resided on end-caps and phosphor powders detached from the breaking and washing steps. The TCLP values of simulated all lamp-glasses and samples obtained from recyclers were higher than the limit of LDR standard (0.025 mg/L). After investigating acid treatment and high temperature treatment as mercury reclamation techniques, it was found that heating provided the most effective mercury capture. Although the initial mercury concentrations of individual sample were different, the mercury concentrations after 1 h exposure at 100 degrees C were below 4 mug/g for all samples (i.e., <1% remaining). Therefore, it is recommended that heating be used for recovering mercury from spent fluorescent lamps.